Electric discharge lamp



May 7, 1957 P. scHuLz ETAL 2,791,727

ELECTRIC DISCHARGE LAMP Filed Deo. 9, 1954 fnlaunua Invent Paul Sc z Arnold Bauer l by T eir Attorney magnetic field.

' It is well known in the discharge lamp art to employ a Amagnetic field generated by either a permanent or elec- United States Patent ELECTRIC DISCHARGE LAMP Paul Schulz, Karlsruhe, and Arnold Bauer, Augsburg, Germany, assignors to Patent-Treuhand-Gesellschaft fur elektrische Gluhlampeu m. b. H., Munich, Germany Application December 9, 1954, serial No. 474,176 Claims priority, application Germany December 30, 1953 8 Claims. (Cl. 315-347) The present invention relates to electric discharge lamps and more particularly to high pressure gaseous discharge lamps in which starting of such lamps at the available line voltage is facilitated by the generation of a tromagnet disposed exteriorly of the lamp envelope to stablize the arc discharge, or to shift the latter from its otherwise normal position. In some instances it has also been proposed to employ the conductors for the lamp electrodes for the generation of a magnetic field, to accomplish the same purpose as the exteriorly positioned permanent or electromagnets.

The present invention likewise contemplates-the generation of a magnetic field by the leading-in and supporting conductors but the primary object of using such magnetic field is to facilitate starting of the lamp after which such field performs its previously known purpose.

of stabilizing the discharge or shifting it to a desired position within the lamp envelope. The utilization of a magnetic field to facilitate starting has been found to be particularly desirablel with gaseous discharge lamps havingy a krypton and/or xenon filling at a pressure of several atmospheres, even as high as one hundred atmospheres, because owing to the low potential gradient of the ensuing high-pressure gaseous discharge the operating current intensities and in consequence thereof the magnetic field produced by a simple leading-in and supporting conductor is of considerable magnitude.

Discharge lamps of this type are accordingly provided by the present invention in which the arc discharge is inuenced by a magnetic field generated by the leading-in and supporting conductors for the spaced electrodes within the lamp envelope. -In addition, such leading-in and supporting conductors are provided with a small section spaced in close proximity to each other for the purpose of initiating a discharge at such section upon the application of line voltage to the lamp, while the remainder of such leading-in and supporting conductors are spaced apart a distance suiiicient to prevent the formation of a discharge therebetween particularly when it is borne in mind that such leading-in and supporting conductors are constructed of a material, coated or covered, so as to not be electron emissive and thus not conducive of the formation of a cathode spot.- Also, these leading-in and supporting conductors are so disposed within the lamp envelope that the magnetic field generated thereby relative to the direction of current ow, upon initiation of an arc discharge between the closely spaced sections of the leading-in and supporting conductors, causes such arc discharge to travel or be transposed along the conductors to the spaced electron emissive electrodes where such arc discharge remains during operation of said lamp.

By providing the leading-in and supporting conductors with the section spaced in close proximity to each other, or as a modification interposing a starting electrode therebetween, the required starting voltage is propor- 2,791,727l lPatented May '7, 1957 2 tionately low. This is important especially since it is recognized that with high-pressure gaseous discharge lamps generally the starting voltage is very high due to the high pressure existing in such lamps even under cold non-operating conditions and that this starting voltage becomes higher with an increase in the spacing across which the arc discharge path must travel. By means of the particular shape of the leading-in and supporting conductors provided by the present invention, the arc,` as previously mentioned, does not remain at the closely spaced section of the conductors or between the starting electrode and a conductor where it is first initiated but such arc is forced to travel along the leading-in and supporting conductors tothe most distantly spaced ends thereof which serve as the electrodes or are specifically provided with electron emissive electrodes. v f

Also, as previously mentioned, it is essential thatap- 'propriate steps be taken to eliminate the possibility'o'f the arcpdischarge remainingat the section of the vconductors in close proximity to each other where it is initiated. Such'steps accordingly comprise the selection of a material for the leading-in conductors, such as the highly refractory metals of tungsten or tantalum, as well as zirconium, and making them of sutiicient cross-section that heat is readily dissipated so that a cathode spot cannot be formed or by coating or covering the leading-in and supporting conductors with a suitable non-emissive material. It is also highly desirable that the small sections of the leading-in and supportingconductors in close proximity to each other, or the starting electrode if employed, where the discharge is initiated, be positioned to one side of the discharge path between the electrodes or below the operating electrodes. In this manner the convection currents arising from initiation of the arc discharge willassist the traveling of the arc from its place of Yorigin to the operating electrodesl and preclude any tendency for the' arc to. travel in an opposite direction, since it must accordingly travel either vertically orhorizontally. In the event of proportionately low operating current intensity the magnetic field produced by theA leading-in and supporting conductors is too weak to definitely assure the transposition of the arcv discharge from'the section where it is initiated to the operating electrodes, then such current intensity may be suitably increased even to a Value higher than the final-operating current intensity and'maintained at such increased value until the arc discharge has completed its travel from the point of origin to thel operatingelectrodes;

-The present invention in `one of its modifications also eliminates the necessity for an external startingswitch by providing a switching arrangement operable entirely automatically and positioned within the lamp envelope. Por example, fone lof the leading-in and supporting conductors carrying a first operating electrode at its end is provided with the aforementioned small section inclose "ice vproximity to the other leading-in conductor which secvdischarge is thus initiated between the leading-in and supporting conductor for the yfirst operating electrode and this auxiliary electrode and then travels -to the first oper- -ating electrode until it Aflashes over to the second operating electrode which has a special electric current leadingin conductor. Transfer of the discharge from between the first operating electrode and ,the auxiliary electrode over to between the two operating electrodes is also facilitated if the second operating electrode is at a slightly higher potential than that applied to the auxiliary elecnode. From the fregslng it thus bewmesjraaiiy apparent that not only is an external starting switch "eliminated for starting the lamp but the internal switching over of the arc dischargecan' be utilized if desired to automatically connect an additional external magnetic field generatorv into lthe arrangement. v n

The foregoing descriptionV of the present invention may be better appreciated by reference to the accompanying drawings showing various embodiments of the invention Whsrenr Figure 1 shows a cross-sectionalview of a high-pressure gaseous discharge lamp of the present invention designed particularly for vertical operation,

Fig". 2 is a cross-sectional view taken on the line lI-Il ofFig.1, l Y.

Fig. 3 is` a.,oross-secti'onal` View somewhat similar to Figa but' showing a slight modification which the lamp of the present invention may talee,

Fig.A 4 shows another modification which the lamp of 'thep'resent invention maytalteand designed more partic'njlarly for horizontal operation, 1, l i

Fig. 5Vv is a longer arc-discharge lamp of the present invention and thus an additional modification thereof,

Fig. 6 is 'a cross-sectional view taken on the line VI-VI of Fig.,5, y n v Fig'. 7 is a side view of another modification of a h orizontal operating lamp' made in accordance with the present invention, n

Fig. 8 is a sectional view showing the positionof the pole shoes of Fig. 7 relative to the lamp and the ensuing arc discharge,` i.

Fig. 9 is a still further modification of a lainp designed in accordance with the present invention for horizontal oper-ation.v y Referring now to the drawing in detail, the high-presjsure gaseous discharge lamp as shown in Fig. 1 comprises van envelope 1 of quartz orv similar high-nielting point glass which is filled with krypton and! or xenon to a pressure of about y3 yto 10 atmospheres at vambient rtem-perature. The leading-:in wires 3, 4 and 5 are sealed vacuurntight through the stem 2V In the interior Iof the envelope 1` these leading-in wiresare connected to supporting fconductorsncarrying electrodes or themselves constitut'ing electodes. For example, the supporting conductor 6 is connected to leading-'iny wire?? Yand its free inner end 7 servesras an operatingelectrode,A while supporting conductor 8, with its free inner end V9 serving as another operating electrode 9, is connected to leading-in As ,shown in Fig. 1, the conductor 8 is provided with a small section 171 spacedin close proximity to a point 10 on conduct-or 6 compared with the much greater spacingbetweentheelectrodes v'7 and 9, YThis short gap 'between the conductors 6 and `8 at the points 10 and 11 facilitates the initiation of a discharge with 'a proportionally low voltage but in addition an auxiliary electrode 12 connected to the` leading-in ,wire 4 may be provided, if desired. Following initiation of the arcdischarge between the points10 and 11, with attend-ant current flow through the conductors 6 andf8, a magnetic field is generated by such conductors which causes the arc discharge to travel along these conductors 6 and 8 until it is transposed to the electrode ends 7 Vand 9 where thedischarge remains during continued operation of the lamp. Inrthis particular embodiment of the present inventionthe travelling of the arc discharge is facilitated by convection currents since the discharge is initiated below the operating electrodes causing the upward ti-ow of yconvection currents. Moreover, the leading-in and supportingcnductors 6 and 3 throughout their length, other `than lat the points 10 and 11are spaced apart a distance siiiiicient to prevent the formation of a cathode spot 'and are of a material, such as tungsten, tantalurn Ior zirconium which is not conducive to the formation of a cathode spot at the available voltage, or if preferred the supporting conductors may be coated or covered with a non-electron emissive material.

It will also be noted from Fig. 1 that the 4conductors 6 and 8 are so positioned within the envelope 1 that the electrode ends 7 and 9 are disposed in a channel formed lby a longitudinal recess 13 in the envelope wal'i, so that the ensuing discharge between these operating electrodes 7 Iand 9 will be more or less restricted to this channel recess 13 at one side of the lamp. Such restriction of the arc discharge likewise will restrict the blackening 4of the envelope by electrode deposits to this channel Iand perhaps to the top 14 of the envelope so that the remainder of the envelope wall being further away from this channel remains substantially free of deposits `and hence radiation of light or, in a particular case, of invisible radiation will not be impaired during l-a'rnp life. To further protect the top of the envelope 14 from' blackening a screen 15 may also be employed. In order to restrict envelope blackening it ris not entirely essential to provide the envelope with the longitudinal recess 13 since an arcuate sleeve 16 extending longitudinally of the envelope 1, as shown in the modification of Fig. 3, will accomplish the same purpose.

In the ca se of high pressure gaseous discharge lamps primarily intended for horizontal operation of the arc discharge the present invention may be utilizedrin the manner shown in Fig. 4. Here again the supporting conductors 6 and 8 are shown with their points 10 and 11 in close proximity to each other for initiating the discharge in the same manner as above mentioned with respect to the embodiment shown in Fig. l. Accordingly, the arc discharge will likewise travel under the influence of the magnetic field created by the conductors 6 and 8, or the leading-in wires Sand 5, through which current is flowing along the leads until such discharge is ytrarisposed to the electrode ends 7 and 9 where it remains during continued operation of the lamp as above described. The repelling effect of the magnetic force to the conductor 6 and of the arc i7 will tend to suppress the convection effect which urges the highly heated andy lighter arc gases in an upward direction. Thus by appropriate control it is possible to raise horizontal arc discharges upwardly several millimeters into a much stablerA operating position than is possible with vertically operating arc discharges under the same circumstances.

A lamp is shown in the modification of Fig. 5 in which initiation and stabilization of a long arc discharge is obreasons, a high pressure gaseous discharge lamp with a rare gas filling would not allow voltage ranges above 30 to 40 volts without stabilization of the envelope wall. In Fig. 5 an upward directed force results from the effect of the magnetic field from conductor 6 on the arc between the electrodes 7 and 9 whereas the arc is also urged downwardly by the magnetic field created by the conductors 18 provided above the lamp, as shown more clearly in Fig. 6. Accordingly, the present invention provides a means for obtaining an equilibrium so that the arc will H burn stably in the tube axis and an overloading of the upper zones of the lamp envelope is prevented or, conversely, a higher loading is possible than can be obtained with wall-stabilization.

As shown in Fig. 6 the parallel arranged conductors 18 are provided on a cylindrical jacket around the arc as axis. This arrangement of the conductorsA 18 is of importance for the purpose of preventing' urging of the arc to one side of its true axis between the electrodes. AA similar magnetic field may also be produced'in the form of a channel by providing electromagnets 19 with yelongated po'le pieces 20, as shown in Fig. 7. The coils 21 having a few windings through which lamp current ows will produce a uniform magnetic field corresponding to the arc length, as indicated by the arrows as shown in Fig. 7. Fig. 8 shows in a sectional view, the position of the pole pieces 20 relative to the lamp envelope 1 and the arc discharge 17 so that as little of the light fiux of the arc is absorbed as possible.

Referring again to Fig. the arc discharge is initiated between the points and 11 of the conductors 6 and 8 as before explained but in this instance it is produced by the higher potential impressed across the auxiliary electrode 12. Such starting of the arc discharge may be also effected by opening a starting contact carried by a bimetallic strip or by a magnetically operable switch or should it be preferred the discharge may be started by application of a sufliciently high enough voltage directly across the main electrodes 7 and 9. Once started, the arc discharge at point 10 on conductor 6 (Fig. 5) is forced by the previously described magnetic field along the conductor 6 to its main electrode end 7. However, in order for the magnetic field of the conductors 6 and 8 to be effec-tive, the opposing magnetic field created by the conductors 1S has to be removed by closing switch 22 and thus short-circuiting a portion of choke coil 23 which increases the current of the discharge and hence the internal magnetic field. It is also possible to utilize the magnetic field from the conductors 18 to assist the internal field in transposing the arc discharge from its point of origin to the operating electrodes 7 and 9, if desired, by providing a pole changing switch as can be readily understood.

It is also not absolutely essential to provide the special switch 22 for the outer lmagnetic field if, as shown in Fig. 9, the arc is first started between the cur-rent conductor of only one operating electrode and an auxiliary electrode from which it is subsequently transposed to the most distant operating electrode. This modification, as shown in Fig. 9, is for a horizontal operating lamp 1 which again is provided with the main operating electrodes 7 and 9, in this instance are carried by supporting conductors 11 and 25. Adjacent to the operating electrode 9 or to the supporting conductor 11 is the closely spaced section 10 of the conductor 6, the end of which constitutes an auxiliary electrode 24, and the additional starting electrode 12 may again be provided between the sections 10 and 11 as previously described relative to Fig. 5.

The arc discharge initiated between the sections 10 and 11 likewise travels, under the influence of the magnetic field created by the leading-in and supporting conductors 6 and 11, along the auxiliary electrode until it reaches the end thereof 24 from whence it flashes over to the operating electrode 7. For increasing the strength of the magnetic field generated by the conductors 6--10 and 11, the current intensity may be raised by the provision of a tap 26 connected to the choke coil 273. Also, a lhigher potential may be impressed across the operating electrodes 7 and 9 than between the main electrode 7 and the auxiliary electrode 24, by connecting the operating electrode 7 to the free end of the choke coil 23 since both winding sections 27 and 28 are then in circuit so that the entire choke 23 thus acts as a transformer increasing the potential above that produced by only the choke section 27 alone, to which the auxiliary electrode 24 is connected. Also, as soon as the arc discharge is transposed from the auxiliary electrode 24 to the operating electrode 7, the current intensity of the arc is automatically decreased because it is restricted by the full windings of the choke coil 23.

nected in circuit with operating electrode 7, has no effect on the internal magnetic field created by the conductors 6-10 and 11 because this winding 18 is inoperative until the arc discharge is transposed to operating electrode 7 at which time such winding 18 only then becomes automatically operative.

From the foregoing it should thus become obvious to those skilled in the art that a high pressure gaseous discharge lamp has been provided by the foregoing in which a magnetic field is utilized to facilitate starting of such lamp at a low voltage. Moreover, such magnetic field is created by the positioning of the leading-in and supporting conductors which field is of sufficient magnitude as to cause the discharge, once it is initiated, to be very rapidly transposed to the main operating electrodes.

It is also -to be understood that while several embodiments of the present invention have been. shown and described, still further modifications thereof may be made without departing from the spirit and scope'of the appended claims.

We claim:

1.7An electric high-pressure gaseousdischarg'emlamp comprising an envelope provided with spaced electron emissive electrodes therein between which a discharge occurs during operation of said lamp, leading-in and electrode-supporting conductors within said envelope of less electron emissivity than said electrodes and having a small portion thereof in close proximity to each other to initiate a discharge upon the application of a voltage -to said lamp between said closely spaced portions, with the remainder of said leading-in and supporting conductors spaced apart a distance sufficient to prevent the formation of a discharge therebetween; and said leadingin and elecfrode-supporting conductors being so positioned relative to each other that, upon initiation of the discharge with the attendant direction of current flow therethrough relative to the discharge, a magnetic field is generated between such leading-in and electrode-supporting conductors, which causes the discharge-to be. transposed from 'the closely spaced discharge initiating portion of said leadingin and electrode-supporting conductors, to the spaced Aelectron emissive electrodes where the discharge remains during operation of said lamp.

2. An electric high-pressure gaseous discharge lamp comprising an envelope having a base and'provided `with spaced electron emissive electrodes therein between which a discharge occurs during operation of said lamp, leadingin and electrode-supporting conductors within said envelope of less electron emissivity than said electrodes and having a small portion thereof in close proximity to each other and located between said base and lthe most adjacent electrode to initiate a discharge upon the application of a voltage to said lamp between said closely spaced portions, with lthe remainder of said leading-in and supporting conductors spaced apart a distance suicent. to prevent the formation of a discharge therebetween; and said leading-in and electrode-supporting conductors being so positioned relative to each other that, upon initiation of the discharge with the attendant direction of current ow therethrough relative `to the discharge, a magnetic field is generated between such leading-in and electrodesupporting conductors which causes the discharge to be transposed from the closely spaced discharge initiating portion of said leading-in and electrode-supporting conductors to the spaced electron emissive electrodes Where the discharge remains during operation of said lamp.

3. An electric high-pressure gaseous discharge lamp comprising an envelope provided with spaced electron emissive electrodes therein between which a discharge occurs during operation of said lamp, leading-in and electrode-supporting conductors within said envelope of less electron emissivity than said electrodes andhaving a small portion thereof in ,close proximity toeachother and located to one side of the discharge path between said electrodes to initiate a discharge upon the application of t 7 ai vilt'ge to .said lamp between said closely spacedY portions, the remainder of 'said leading-inY and supportetois spaced apart a distance sutncint to prevent the formation of a discharge therebetween; and said leading-in and electrode-supporting conductors being so positioned relative to each other that, upon initiation ofth'etdischargc with the attendant direction of current ow therethrough relative to the discharge, a magnetic field is generated between such leading-in and electrodes'up'porting conductors, which causes the discharge to be trans/posed from the closely spaced discharge initiating portion of said leading-in and electrode-supporting condoctors, to the spaced electron emissive electrodes where the discharge remains during operation of said lamp.

4. An electric high-pressure gaseous discharge lamp comp' sing an envelope provided with spaced electron ennssive electrodes therein between which a discharge occurs during voperation of said lamp, leading-in and electrode-supporting conductors within said envelope of less electron emissivity than said electrodes and having a small portion thereof in close proximity to each other, a starting electrode adjacent said small closely spaced portion' to initiate a discharge upon the application of a voltage to said lamp between said starting electrode and the closely spaced portion of one of said leading-in and electrodefsupporting conductors, with the remainder of said leading-in and supporting conductors spaced apart a distance suicient to prevent the formation of a discharge therebetween; and said leading-in and electrodesupporting conductors being so positioned relative to each other that, upon initiation of the discharge with the lattendant direction of current ow therethrough relative to the discharge, a magnetic iield is generated between suchHleading-in and electrode-supporting conductors, which causes the discharge to be transposed from the starting electrode andthe adjacent closely spaced discharge linitiating portion of said leading-in and electrode-supporting conductors, to the spaced electron emissive electrodes where the discharge' remains during operation of said lamp.

Y5.v An electric high-pressure gaseous discharge lamp comprising an envelope provided withV spaced electron voltage to said lamp between said detlectable starting electrode aii'cl the closely spaced portion oi one of said leading-in and electrode supporting conductors, with the remainder of said leading-in and supporting conductors spaced apart a distance sutlicient to prevent the formationjof a discharge therebetween, and said leading-in and 'electrode-supporting conductors being so positioned relative to each other that, upon initiation of the discharge with the attendant direction of current flow therethrough relative to the discharge, a magnetic held is generated between such leading-in and electrode-supporting conductors, which causes the discharge to be transported from the defiectable starting electrode and the adjacent closely spaced discharge initiating portion of said leading-in and electrode-supporting conductors, to the spaced electron emissi've electrodes where the discharge remains during operation of said lamp.

6. An electric high-pressure gaseous discharge lamp comprising an envelope provided with a longitudinal groove in the Wall thereof, spaced electron emissive velectrodes positioned` adjacent each end of said groove between which a discharge occurs during operation of said lamp, leading-in fand electrode-supporting conductors within =said envelopeuofvless electron emissivity thanrsaid electrodes and-having a small portion thereof in close proximity to each other to initiate a discharge upon the 8 application of a voltage to said lamp between said closely spaced portions, with the remainder of said leading-in and supporting conductors spaced apart a distance suiiicicrit to prevent the formation of a discharge therebetween, and said leading-in and electrode-supporting conductors being so positioned relative to each other that, upon initiation of the discharge with the attendant direction of current ow therethrough relative to the discharge, a magnetic field is generated between such leading-in and electrodesupporting conductors which causes the discharge to be transposed lfrom the closely spaced discharge initiating portion o'fvsaid leading-in and electrode-supporting conductors to the spaced electron emissive electrodes in said longitudinal groove where the discharge remains during operation of said lamp.

7. An electric hig`hpressure gaseous discharge lamp comprising an envelope provided with spaced electron eniissive electrodes therein between which a discharge occurs during operation of said lamp, leading-in and electrode-supporting conductors within said envelope of less electron cinissivity than said electrodes and having a small portion thereof in close proximity to each other to initiate a discharge upon the application of a voltage to said lamp between said closely spaced portions, with the remainder ot said leading-in and supporting conductors spaced apart a distance suthcient to prevent the formation of a discharge therebetween, and said leading-in and electrodesupporting conductors being so positioned relative to' each other that, upon initiation of the discharge with the attendant direction of current flow therethrough relative to the discharge, a magnetic held is generated between such leading-in and electrode-supporting conductors which causes the discharge to be transposed from the closely spaced discharge initiating portion of said leading-in and electrode-supporting conductors to the spaced electron emissive electrodes where the discharge remains during operation of said lamp, and means disposed exteriorly of said lamp for generating a magnetic eld of opposite direction to the magnetic eld generated by said interiorly disposed leading-in and electrode-supporting conductors, to cause stabilization of the discharge within said envelope between said magnetic fields.

8. An electric high-pressure gaseous discharge lamp comprising an envelope provided with spaced electron emissive electrodes therein between which a discharge occurs during operation of said lamp, leading-in and electrode-supporting conductors within said envelope of less electron emissivity than said electrodes and having a small portion thereof in close proximity to each other to initiate a discharge upon the application of a voltage to said lamp between said closely spaced portions, with the remainder of said leading-in and supporting conductors spaced apart a distance sutiicient to prevent the formation of a discharge therebetween, and said leading-in and electrodesupporting conductors being so positioned relative to each other that, upon initiation of the discharge with the attendant direction of current how therethrough relative to the discharge, a magnetic field is generated between such leading-in and electrode-supporting conductors which causes the discharge to be transposed from the closely spaced discharge initiating portion of said leading-in and electrode-supporting conductors to the spaced electron emissive electrodes where the discharge remains during operation of said lamp, and magnetic-eld-producingconductors extending longitudinally of the envelope exterior and in an arcuate plane partially about said envelope for generating a magnetic tield with the ensuing arc discharge within said envelope as the axis for the arcuately disposed magnetic-held producing exterior conductors.

References Cited in the tile of this patent UNITED STATES PATENTS '1,945,325 Machen Jan. 3o, 1934 weiters Mathieu s June s, 1934 2,663,823 Elenbaas et al. Dec. 22, 1953 

